KEY TAKEAWAYS
- The phase II ATREZZO trial examined the combination of atezolizumab, trastuzumab, and vinorelbine in pts with specific HER2+ ABC subtypes.
- The study’s primary endpoint was assessing the overall response rate (ORR).
- The first phase of ATREZZO achieved its predetermined endpoint.
The phase II ATREZZO study investigated the combination of atezolizumab, trastuzumab, and vinorelbine in patients (pts) with HER2+ ABC that are either ER– or ER+ with PAM50 non-luminal subtypes. The eligibility requirements included previous progression on trastuzumab and an antibody drug conjugate and the presence of measurable disease.
The primary objective was to measure the overall response rate (ORR). Tumor samples were essential to determine the PAM50 and PD-L1 IHC (SP142) status. Following Simon’s two-stage design, after evaluating the first 19 patients, the study would proceed to recruit 55 patients if at least 3 showed an objective response, aiming for an ORR ≥ 13%. Eligible pts were those who had taken at least one treatment dose and had one postbaseline tumor assessment.
In the study, 61 pts were initially screened, identifying 42 tumors that were either ER+ and non-luminal or ER-. Of these, 23 pts were included, with 19 being assessed for the primary objective. Baseline pts characteristics included a median age of 58 years (range: 33-72), 32% (6/19) being ER+, 90% (17/19) having visceral disease, a median of 3 (range: 1-4) prior treatments for ABC, and 16% (3/19) having PD-L1 IHC positive tumors.
By the data cut-off in February 2022, 14 pts had terminated their treatment due to disease progression and one because of adverse effects. Four pts remained under treatment. The ORR stood at 31.6% (6/19, 95% CI 12.59-56.57), achieving the predetermined ORR for the trial’s first stage. Adverse events of grade 3-4 were reported in 42.1% of the patients (8/19).
The first phase of the ATREZZO trial met its set benchmark. The study’s second phase will involve the recruitment of up to 55 pts to further gauge the efficacy of this drug combination in this patient subset. Related studies are ongoing and will be shared at the meeting.
Clinical Trial: https://classic.clinicaltrials.gov/ct2/show/NCT04759248
Ciruelos, E.M., Ortega, P. T., Bofill, F.J.S., Santiago, S.G., Miro, C.R.A., Escrivá-De-Romaní, S., González, A.P., Simon, S.P., Ponce, J., Martínez-Sáez, O., Cejalvo, J.M., Martorell, A.P., López-Barajas, I.B., Guerra, J.A., Torres, E.S., Sanchez, C.A.R., Villanueva, L., Villacampa, G., Prat, A., Pascual, T. ATREZZO TRIAL (SOLTI-1907) A PHASE II TRIAL TARGETING ESTROGEN RECEPTOR NEGATIVE OR PAM50 NON-LUMINAL DISEASE WITH ATEZOLIZUMAB IN COMBINATION WITH TRASTUZUMAB AND VINORELBINE IN HER2-POSITIVE (HER2+) ADVANCED BREAST CANCER (ABC): INTERIM ANALYSIS. Annals of Oncology (2023) 8 (1suppl_4): 101223-101223. 10.1016/esmoop/esmoop101223
